In the modern society, the use of electronic products has become an indispensable part of the life, and necessities such as eating, clothing, living, traveling, teaching, and entertainment are correlated to electronic products. Generally, a consumption type product is configured with one or a plurality of keys. To improve usability of a key, one or a plurality of backlight units is configured on a circuit board of the key, so that a user may use the electronic product in relatively poor light source environment, or a prompt of the key may be provided for the user by means of a backlight unit.
However, in a process of manufacturing or using an electronic product, static electricity may be gradually accumulated in the electronic product. Once an electrostatic discharge (ESD) effect appears, a backlight unit or other electronic elements disposed on the circuit board may be damaged, to further influence the functions of the circuit, so that the electronic product cannot operate normally.
To prevent electrostatic discharge from damaging a backlight unit or other electronic elements disposed on a circuit board, an existing technical document, for example, the U.S. Pat. No. 6,323,445B1, provides a membrane switch structure with electrostatic discharge protection. The membrane switch structure includes three layers of insulation material. The ESD protection circuit pattern may at least copy the whole or a part of the conductive circuit pattern. The Taiwan patent no. TWI578350 provides a key and a keyboard using the same with electrostatic discharge protection. The circuit board includes: an upper membrane layer, a lower membrane layer, a spacer layer, a first conductive layer, and a second conductive layer. The first conductive layer is located between the lower membrane layer and the spacer layer; and the second conductive layer is located between the upper membrane layer and the spacer layer. In addition, the first conductive layer is electrically connected to the second conductive layer through a wire, and the second conductive layer is in contact with the grounding arm disposed on the baseboard, so as to conduct the static current that hits the first conductive layer to ground. However, in the existing technology, the electrostatic discharge protection circuit pattern is mostly disposed in an area overlapped with the spacer layer. Such the configuration may increase the thickness of the membrane circuit board, and in another aspect may influence the configuration of the key switch circuit. Moreover, additionally configuring a grounding arm may probably increase the complexity of manufacturing a key structure, resulting in reduction of the efficiency and yield of electronic product manufacturing.
Therefore, how to provide a key structure capable of rapidly and effectively conducting static electricity to ground and meanwhile reducing the complexity of manufacturing a key structure and the thickness of the circuit board is a technical matter to be resolved in the present invention.